Variable magnification lens having image stabilizing function

ABSTRACT

An image stabilizer for stabilizing an image against unexpected vibrations or shaking of a zoom lens includes a diaphragm arranged to vary its full-open aperture diameter according to a magnification varying (zooming) action from a wide-angle end position to a telephoto end position of the zoom lens for the purpose of preventing variations in light quantity which more conspicuously take place in the peripheral part than in the central part of an image plane when an image stabilizing action is performed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical apparatus having afunction of correcting image shakes caused by changes of relative anglesof an object to be photographed and the optical apparatus.

[0003] 2. Description of Related Art

[0004] Optical apparatuses of the kind arranged to be capable ofcorrecting image shakes have heretofore been developed in variedmanners. FIG. 7 shows an example of such optical apparatuses. In thecase of the optical apparatus shown in FIG. 7, the so-called variableangle prism 100 is arranged in front of an optical system composed oflens units 101 to 104 and a diaphragm 105 to correct the image shakesbefore a light flux P from an object comes to be incident on the opticalsystem. Referring to FIG. 7, the lens units 101 to 104 and the diaphragm105 are supported by a fixed tube 105. An image sensor 107 is arrangedto convert into an electrical signal an optical image formed on a focalplane which is located in rear of the fixed tube 106.

[0005] In the above optical apparatus, however, the variable angle prism100 is disposed in a place where the width of the light flux P passingthrough the optical system becomes widest. Therefore, the arrangementfor having the variable angle prism 100 in that position isdisadvantageous in respect of reduction in size of the opticalapparatus.

[0006] In view of the above problem, some of known optical apparatuseshave been developed to permit reduction in size. For example, an opticalapparatus is arranged to have the variable angle prism disposed betweentwo lens units within an optical system composed of a plurality of lensunits. Another optical apparatus which is of the type called a lensshift type is arranged to correct the image shakes by moving some of aplurality of lens units in a direction perpendicular to an optical axis.Some other optical apparatus has been developed to have an electronicimage-shake correcting function called an electronic image stabilizingdevice which corrects image shakes in the following manner. A CCD whichhas a larger area than an actually necessary area as an image sensor(thus requiring use of a large optical system having an image circlecovering the whole surface of the CCD) is arranged to correct imageshakes by varying the reading position thereof according to informationon image shakes detected.

[0007] With the conventional optical apparatus arranged as describedabove, for example, in an optical system composed of lens units 111 to114 having positive, negative, positive and positive refractive powers,respectively, and a diaphragm 115, as shown in FIG. 8, while an on-axiallight flux “a” passes the center of the optical system, the upper andlower parts of an off-axial light flux “b” are blocked by the effectivediameters, indicated by arrows A and B, of the lens units 111 and 114.Therefore, the thickness of the light flux becomes smaller accordinglyas the incident angle of the light flux is larger (corresponding to theperiphery of an image plane). As a result, an image formed by the lightflux on an image forming plane 116 rapidly becomes darker in itsperipheral part. The peripheral light quantity of the light flux is thusdecreased by the so-called vignetting phenomenon.

[0008] In the case of the above-stated function of optically correctingimage-shakes by deflecting a light flux within the optical system, ifthe optical apparatus is arranged to correct the image shakes in such away as to have an object image not moving on the image forming plane atthe time of a change of relative angles of the object and the opticalapparatus, the vignetting degree of the light flux at each point of anobject image on the image forming plane would vary to change the lightquantity distribution of the object image, as the relative angles of theobject and the optical apparatus have changed.

[0009] Such a state is explained with reference to FIG. 9. In FIG. 9,image forming positions are shown on the abscissa axis and the luminanceof the image is shown on the ordinate axis. A one-dot-chain line shownin FIG. 9 represents the initial distribution of light quantity obtainedbefore the relative angles of the object and the optical apparatuschange. Full lines “a” and “b” shown in FIG. 9 represent light quantitydistributions obtained with image shakes corrected when the relativeangles change, for example, alternately to the right and to the left.When image shakes which actually take place continuously are correctedin this manner, although the object image is corrected to be not movingon an image plane, the image shake correction results in variations ofluminance of the picture taking place in synchronism with the imageshakes. The luminance variations become salient particularly in theperipheral part of the image plane. As a result, the quality of an imagethus obtained degrades to an unacceptable degree.

[0010] Further, the electronic image shake correcting function also hasa problem similar to that of the optical image shake correctingfunction. In this case, the light quantity distribution on the imageforming plane does not change, since the relation between the imageforming plane 116 and the optical system which is composed of the lensunits 111 to 114 and the diaphragm 115 as shown in FIG. 8 is unchanging.However, when the object image is caused to move by the change ofrelative angles of the object and the optical apparatus, the readingposition also changes following the movement of the object image, forexample, as indicated by reading positions I and II in FIG. 10. Thechange of the reading position then brings about the same phenomenon asin the case of the optical image shake correcting function.

BRIEF SUMMARY OF THE INVENTION

[0011] The invention is directed to the solution of the prior artdescribed above. It is, therefore, an object of the invention to providean optical apparatus arranged to be capable of giving an easily viewableimage of high quality by alleviating luminance variations which occur inthe peripheral parts of an image plane in correcting image shakes and bylessening a luminance difference between central and peripheral parts ofthe image plane, particularly at a part in the neighborhood of atelephoto end position where the variations of luminance becomeconspicuous.

[0012] To attain the above object, an optical apparatus according to theinvention is arranged to have the following features.

[0013] (1) The full-open aperture diameter of a diaphragm provided forcontrol over the quantity of a light flux passing through a variablemagnification optical system having an image shake correcting functionis limited according to the focal length.

[0014] (2) An on-axial light flux in the neighborhood of the telephotoend position of the variable magnification optical system which takestherein an off-axial light flux as well and the on-axial light flux islimited by a diaphragm.

[0015] (3) The on-axial light flux is limited by an auxiliary diaphragmwhich is disposed close to a main diaphragm arranged to determine anF-number.

[0016] (4) The amount of shift of a lens unit to be shifted in adirection perpendicular to an optical axis is corrected according toinformation on the position of the variable magnification optical systemin such a way as to cancel a movement of an image caused by a tilt ofthe variable magnification optical system by the shift of the lens unit.

[0017] The above and other objects and features of the invention willbecome apparent from the following detailed description of preferredembodiments thereof taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0018]FIG. 1 shows a state obtained at a telephoto end position of avariable magnification optical system of an optical apparatus accordingto a first embodiment of the invention.

[0019]FIG. 2 shows a state obtained at a wide-angle end position of thevariable magnification optical system of the optical apparatus accordingto the first embodiment of the invention.

[0020]FIG. 3 is a graph for explaining a light quantity distribution inthe optical apparatus according to the first embodiment.

[0021]FIG. 4 is a graph for explaining the variation of the lightquantity distribution in the optical apparatus according to the firstembodiment of the invention.

[0022]FIG. 5 schematically shows the arrangement of an optical apparatushaving an image shake correcting function according to the invention.

[0023]FIG. 6 is a graph for explaining the limitation of the full-openaperture diameter of a diaphragm according to the focal length in theoptical apparatus shown in FIG. 5.

[0024]FIG. 7 is a longitudinal sectional view of the conventionaloptical apparatus having an image shake correcting function.

[0025]FIG. 8 is a diagram for explaining how the quantity of light dropsin the peripheral part of an image plane due to vignetting.

[0026]FIG. 9 is a graph for explaining the variation of the lightquantity distribution.

[0027]FIG. 10 is a graph for explaining the variation of the luminanceon an image plane in the case of electronic image stabilization.

[0028]FIG. 11 is a sectional view showing essential parts of a zoom lensfor a video camera to which the invention is applied as a secondembodiment thereof.

[0029]FIG. 12 is an exploded perspective view showing a zoom lens barrelshown in FIG. 11.

[0030]FIG. 13 is an exploded perspective view of an image shakecorrecting unit mounted on the zoom lens shown in FIG. 11.

[0031]FIG. 14 is a plan view showing a first diaphragm means included inthe zoom lens shown in FIG. 11.

[0032]FIG. 15 is a plan view showing a second diaphragm means includedin the zoom lens in FIG. 11.

[0033]FIG. 16 is a graph for explaining the variation of a peripherallight quantity in a case where the second embodiment is not providedwith the second diaphragm means.

[0034]FIG. 17 is a graph for explaining the variation of a peripherallight quantity in a case where the second embodiment is provided withthe second diaphragm means.

[0035]FIG. 18 is a block diagram showing a system for image shakecorrection control and diaphragm control arranged in the secondembodiment.

[0036]FIG. 19 is a plan view showing a diaphragm means arranged in athird embodiment of the invention.

[0037]FIG. 20 is an exploded perspective view showing a zoom lens barrelaccording to the third embodiment of the invention.

[0038]FIG. 21 is an illustration of a light-quantity control device usedin a different embodiment of the present invention.

[0039]FIG. 22 is an illustration of a light-quantity control device usedin a still different embodiment of the present invention.

[0040]FIGS. 23A and 23B are diagrams showing light-quantitydistributions.

[0041]FIG. 24 is an illustration of a light-quantity control device in afurther different embodiment of the present invention.

[0042]FIG. 25 is a diagram showing light-quantity distribution.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, preferred embodiments of the invention will bedescribed in detail with reference to the drawings.

[0044]FIGS. 1 and 2 show a variable magnification optical system havingan image shake correcting function according to a first embodiment ofthe invention. The variable magnification optical system is composed oflens units 1 to 4 having positive, negative, positive and positiverefracting powers, respectively. In FIG. 1, the variable magnificationoptical system is shown as in a state obtained with the optical systemat a telephoto end position. FIG. 2 shows the variable magnificationoptical system as in a state obtained with the optical system at awide-angle end position. The lens unit 1 is a fixed lens unit. The lensunit 2 is a variator lens unit which is provided for varying themagnification of the optical system by moving backward and forward. Thelens unit 3 is an image-shake correcting lens unit which is arranged todeflect a light flux by moving (shifting) in a direction perpendicularto an optical axis. The lens unit 4 is a focusing lens unit provided foradjusting focus of the variable magnification optical system by movingbackward and forward. A diaphragm 5 is provided for limiting thequantity of a light flux passing through the optical system. A focalplane 6 is arranged to form thereon an image of a photo-taking object.

[0045] In FIGS. 1 and 2, reference symbols “a” and “b” respectivelydenote an on-axial light flux obtained in the central part of an imageplane and an off-axial light flux obtained in the outermost part of theimage plane, i.e., a peripheral part of the image plane. Referring toFIG. 1, which shows the optical system in a state in which the diaphragm5 is fully opened at the telephoto end position, the on-axial light flux“a” passing the lens unit 1 has its peripheral part greatly blocked bythe diaphragm 5. On the other hand, the off-axial light flux “b” reachesthe focal plane 6 without being blocked by the diaphragm 5. Furtherdetails of this state are as follows.

[0046] In FIG. 3, the image forming positions are shown on the abscissaaxis and the luminance of the image is shown on the ordinate axis. Afull line “c” represents a light quantity distribution obtained on thefocal plane 6 shown in FIG. 1. A two-dot-chain line “d” represents alight quantity distribution obtained when the diaphragm 5 is opened to aposition where it does not block the on-axial light flux “a”. A brokenline “e” represents a light quantity distribution obtained when thediameter of the lens unit 1 is reduced to a size at which only such aportion of the on-axial light flux that can pass through the full-openaperture of the diaphragm as shown in FIG. 1 is allowed to pass. Inother words, with the lens unit 1 arranged to have a large diameter toreceive the on- and off-axial light fluxes in large quantity, at leastthe on-axial light flux is made to be limited by the diaphragm 5. Thisarrangement is made such that a difference in luminance between thecentral and peripheral parts of the image plane is lessened. FIG. 4shows variations of light quantity distribution taking place with theimage shake correction actually performed. Lines or curves c′, c″, d′and d″ show the variations of light quantity distribution obtained withthe diaphragm 5 at its positions where the lines “c” and “d” areobtained, respectively. FIG. 4 clearly shows that the variations takingplace in the peripheral part of the image plane, in particular, isgreatly improved by limiting the full-open aperture diameter of thediaphragm 5, as indicated by variations I and II of luminance.

[0047]FIG. 5 shows in outline the arrangement of the optical apparatushaving the image shake correcting function. For the lens units 1 to 4,the diaphragm 5 and the focal plane 6 shown in FIG. 1, the followingparts are provided as shown in FIG. 5. A fixed tube 7 is arranged tohold the lens unit 1. A moving frame 8 is arranged to hold the lens unit2 in a known bar-sleeve structure to be movable in the direction of theoptical axis by a stepping motor through a known mechanism including arack and a feed screw.

[0048] A shift frame 9 is arranged to hold the lens unit 3 and to bemovable in a direction perpendicular to the optical axis 0 by a guidemechanism (not shown) which is arranged between a holding frame 10 andthe shift frame 9. The position of the shift frame 9 is arranged to bedetermined in the directions of pitch and yaw by a driving means and aposition detecting means which are not shown.

[0049] A moving frame 11 is arranged to hold the lens unit 4 in a knownbar-sleeve structure to be movable in the direction of the optical axisby a stepping motor through a known mechanism including a rack and afeed screw. A known diaphragm device 12 is arranged to support and drivethe diaphragm 5. The diaphragm device 12 is preferably a so-called irisdiaphragm which has a plurality of sickle-shaped diaphragm bladesarranged in a circumferential direction so as to form an approximatelycircular aperture by rotating the plurality of diaphragm blades at thesame time.

[0050] An image sensor 13 is a CCD which is arranged on the focal plane6 to convert an optical image into an electrical signal. A fixed frame14 is arranged to hold the CCD 13 and other moving mechanisms. Anelectrical signal A read out from the CCD 13 is processed into a videosignal by a camera signal processing circuit 15.

[0051] A microcomputer 16 is arranged to control lens driving actions.When a power supply is switched on, the microcomputer 16 causes a focusmotor driving circuit 19 and a zoom motor driving circuit 20 to rotatetheir respective stepping motors for moving the moving frames 11 and 8while continuously monitoring the output of a focus reset circuit 17 andthat of a zoom reset circuit 18. The output of the focus reset circuit17 and that of the zoom reset circuit 18 are inverted respectively wheneach of the moving frames 11 and 8 comes to a predetermined position,where light from a light emitting part of a photo-interrupter disposedat a fixed part is blocked, or allowed to pass at a boundary part, by alight blocking part of each moving frame. After that, with this positionused as a datum position, the number of driving steps of each steppingmotor is counted within the microcomputer 16 to find the absoluteposition of each of the lens units 4 and 2. Information on the focallength can be accurately obtained by this arrangement. A diaphragmdriving circuit 21 is provided for opening and closing the diaphragm 5under the control of the microcomputer 16. The aperture of the diaphragm5 is controlled on the basis of information B on luminance of the videosignal taken in the microcomputer 16. Information on the diaphragmaperture thus obtained is detected by an aperture value detectingcircuit 22 and is supplied to the microcomputer 16.

[0052] By the aperture control operation, the full-open (maximum)aperture diameter of the diaphragm is limited according to the focallength to have some area where the diaphragm is not opened as indicatedby a hatched part of FIG. 6, which shows the focal length on theabscissa axis and the full-aperture diameter of the diaphragm on theordinate axis. Under this aperture control, a difference in luminancebetween the central part and the peripheral part of the image plane canbe kept small, particularly by cutting off the on-axial light flux onthe side of the telephoto end position.

[0053] Although the structure of an optical system is generally arrangedto have a smaller luminance difference between the central part and theperipheral part of an image plane in the telephoto end than in thewide-angle end, an image formed on a image forming plane is caused byone and the same image shake to move to a greater extent in proportionto the focal length in the telephoto end than in the wide-angle end.Therefore, the problem of luminance variations on the image plane causedby actual image shakes becomes more serious at the telephoto end than atthe wide-angle end. This calls for some improvement in light quantitydistribution obtained in the neighborhood of the telephoto end of thelens system.

[0054] The optical apparatus is provided with a pitch angle (verticalslanting angle) detecting circuit 23 and a yaw angle (horizontalslanting angle) detecting circuit 24. Each of these angles is detectedby integrating the output of an angular velocity sensor which, forexample, is a vibration gyro or the like secured to the opticalapparatus. The outputs of the two angle detecting circuits 23 and 24which show information on slanting angles of the optical apparatus aresupplied to the microcomputer 16.

[0055] For moving the lens unit 3 in correcting image shakes, theoptical apparatus is provided with pitch (vertical) and yaw (horizontal)coil driving circuits 25 and 26. Each of the pitch coil driving circuit25 and the yaw coil driving circuit 26 is arranged to generate a drivingforce for the lens unit 3 by the so-called moving coil device in which acoil is disposed at a gap of a magnetic circuit having a magnet.

[0056] A pitch (vertical) position detecting circuit 27 and a yaw(horizontal) position detecting circuit 28 are provided for detectingamounts of shift of the lens unit 3 with respect to the optical axis.Each of the circuits 27 and 28 is arranged, for example, to have a lightemitting element and a light receiving element fixedly opposed to eachother, to have a slit which is formed in the shift frame 9 interposed inbetween these light emitting and receiving elements, and to obtain ashift amount of the lens unit 3 as an electrical signal. The informationon the amount of shift thus obtained is also supplied to themicrocomputer 16.

[0057] The operation of the first embodiment is as follows.

[0058] When the lens unit 3 moves in a direction perpendicular to theoptical axis, a light flux passing there is bent. As a result, theposition of an object image formed on the CCD 13 moves. Themicrocomputer 16 then controls and causes the optical system to move tothe same amount as the movement amount of the image position actuallycaused by the slant of the optical apparatus in a direction opposite tothe direction in which the object image moves. The image shakecorrecting action is thus can be carried on to keep the formed imageunshakable even when the optical apparatus slants to shake the image.

[0059] Within the microcomputer 16, shift-amount signals obtained fromthe pitch position detecting circuit 27 and the yaw position detectingcircuit 28 indicating the shift amounts of the lens unit 3 arerespectively subtracted from inclination signals obtained from the pitchangle detecting circuit 23 and the yaw angle detecting circuit 24indicating the inclinations of the optical apparatus to obtaindifference signals. Then, the pitch coil driving circuit 25 and the yawcoil driving circuit 26 are caused to drive the shift frame 9 accordingto the difference signals. Under this control, the lens unit 3 is drivento make the difference signals smaller, so that the image can be kept atan objective position.

[0060] In the case of the first embodiment, the lens unit 3 which isarranged to be shifted in a direction perpendicular to the optical axisis disposed closer to an image pickup surface than the variator lensunit 2. The moving amount of the image in relation to the amount ofshift of the lens unit 3 comes to vary according to the position of thevariator lens unit 2, i.e., according to the focal length. The amount ofshift of the lens unit 3 is, therefore, decided not merely according tothe optical-apparatus inclination signals obtained from the pitch angledetecting circuit 23 and the yaw angle detecting circuit 24 but iscorrected also according to information on the position of the variatorlens unit 2. The movement of the image due to the slant of the opticalapparatus is thus arranged to be canceled by shifting the lens unit 3 inthis manner.

[0061] In the first embodiment, the aperture position of the diaphragmwhich is arranged to vary the quantity of a light flux passing throughthe optical system is controlled electrically to limit the full-openaperture diameter of the diaphragm according to the focal length. Morespecifically, the full-open aperture diameter of the diaphragm iscontrolled to decrease accordingly as the position of the lens systemshifts from the wide-angle end position to the telephoto end position.In a case where no image shake correcting action is required, therefore,the optical system is usable in a brighter full-open state at itstelephoto end position by removing the limitation on the full-openaperture diameter of the diaphragm. It is also possible to change thearrangement to have some auxiliary diaphragm arranged near to a main(F-number determining) diaphragm to mechanically impose the above-statedlimitation on the full-open aperture diameter in a sate of beinginterlocked with the movement of the variator lens unit 2, as will bedescribed later herein.

[0062] The first embodiment described above makes the image shakecorrection by shifting, in a direction perpendicular to the opticalaxis, the third lens unit of the variable magnification optical systemcomposed of four lens units which are arranged to have refractive powersin the order of positive, negative, positive and positive refractivepowers. However, the type of the optical system and the lens unit to beshifted are not limited to those of the first embodiment describedabove. The invention is applicable also to an optical image shakecorrecting arrangement having a variable angle prism within a variablemagnification optical system and also to an electronic image shakecorrecting arrangement for the so-called electronic image stabilization.More specifically, the invention is applicable also to an apparatusarranged to attain an image shake correcting effect by processing anelectrical signal obtained from an image sensor which is arranged on theimage forming plane to convert an optical image into an electricalsignal.

[0063] In the first embodiment described above, a variable magnificationoptical system having the image shake correcting function is arranged tolimit, according to the focal length, the full-open aperture diameter ofa diaphragm which is provided for controlling the amount of a light fluxpassing through the optical system. By this, a difference in luminancebetween the central and peripheral parts of an image plane can belessened particularly in the neighborhood of a telephoto end position ofthe optical system where the difference becomes salient. Therefore, anoptical apparatus can be arranged to be capable of giving high qualityimages according to the arrangement of the invention.

[0064] A second embodiment of the invention, which is a more concreteexample, is next described below.

[0065]FIG. 11 is a sectional view showing essential parts of a zoom lens(barrel) for a video camera to which the invention is applied as thesecond embodiment. FIG. 12 is an exploded perspective view showing inpart the zoom lens barrel shown in FIG. 11.

[0066] Referring to FIGS. 11 and 12, a fixed tube 201 is arranged tohold a first lens unit L1. A rear tube 202 is arranged to hold alow-pass filter 203. A CCD image sensor which is not shown is mounted inrear of the low-pass filter 203. An image shake correcting unit 204 isarranged to hold a third lens unit L3 which is arranged as a correctionlens to be driven in a direction perpendicular to an optical axis. Theimage shake correcting unit 204 is interposed in between the fixed tube1 and the rear tube 2 and is fixed in position with screws. A secondlens tube 205 is arranged to hold a second lens unit L2 which isprovided for zooming. Two guide bars 206 a and 206 b are arranged to besupported respectively at their front and rear parts by the fixed tube201 and the rear tube 202 and to have the second lens tube 205 movablein the direction of the optical axis. A fourth lens tube 207 is arrangedto hold a fourth lens unit L4 which is provided for focus adjustment. Asin the second lens tube 205, the fourth lens tube 207 is supported alsoby the guide bars 206 a and 206 b to be movable in the direction of theoptical axis. The two guide bars 206 a and 206 b are arranged along theoptical axis and on opposite sides of the optical axis not only to guidethe second and fourth lens tubes 205 and 207 but also to prevent thesecond and fourth lens tubes 205 and 207 from turning around the opticalaxis.

[0067] An IG meter (IG meter unit) 208 is arranged to drive, by means ofan electromagnetic actuator, diaphragm blades 803 and 804 which jointlyconstitute a first diaphragm means, as shown in FIG. 14. The IG meter208 is carried jointly by the fixed tube 201 and the image shakecorrecting unit 204 in a state of being interposed in between them. NDfilters 806 and 807 are mounted on the front side of the diaphragm blade803 and on the rear side of the diaphragm blade 804, respectively. Theaperture diameter of the first diaphragm means is arranged to bevariable according to the quantity of light incident on the CCD(sensor). Diaphragm blades 820 constitute a second diaphragm means. Thesecond diaphragm means is composed of, in the case of the secondembodiment, six diaphragm blades 820. The diameter of an aperturedefined by the diaphragm blades 820 is arranged to be variable accordingto the zooming position of the zoom lens, in such a manner that thequantity of on-axial light and that of off-axial light obtained when theimage shake correcting unit 204 is driven to decenter the third lensunit L3 are balanced with each other by restricting the on-axial lightflux obtained with the optical system on its telephoto side.Incidentally, the first diaphragm means is arranged to substantiallydetermine an F-number of the zoom lens.

[0068] A zoom motor 209 has its driving part and its output screw partheld in one body by means of a U-shaped metal plate. The zoom motor 209is secured to the fixed tube 201 with screws. A rack 210 is mounted onthe second lens tube 205. The second lens tube 205 is arranged to bedriven in the direction of the optical axis with the rack 210 in meshwith the screw part of the zoom motor 209. In this case, anyintermeshing play and any back-lash in the direction of thrust areremoved by a spring 211 which is arranged to urge the rack 210 in thedirection of intermeshing and in the direction of the optical axis.

[0069] A focus motor 212 is arranged in a manner similar to the zoommotor 209 and is secured to the rear tube 202 with screws. A rack 213and a spring 214 are mounted on the fourth lens tube 207, as in the caseof the second lens tube 205. The fourth lens tube 207 is thus arrangedto be driven and moved in the direction of the optical axis with therack 213 and the screw part of the focus motor 212 intermeshing witheach other.

[0070] The racks 210 and 213 respectively have their shaft parts 210 aand 213 a fitted into hole parts 205 a and 207 a which are formed in thesecond lens tube 205 and the fourth lens tube 207 in such a way as toextend in the direction of the optical axis, and are thus arranged to beswingable on the shaft parts 210 a and 213 a with respect to the secondlens tube 205 and the fourth lens tube 207. Therefore, even in a casewhere there is some discrepancy in parallelism among the guide bars 206a and 206 b and the output shafts of the motors 209 and 212, the secondlens tube 205 and the fourth lens tube 207 can be smoothly moved.Further, the racks 210 and 213 are urged in the direction of swing bythe springs 211 and 214 to cause meshing parts of the racks 210 and 213to be in pressed contact with their corresponding motor output screws.The meshing parts of the racks 210 and 213 thus can be reliably meshedwith the male screws of the motor output shafts. In the case of thesecond embodiment, stepping motors are employed as the zoom motor 209and the focus motor 212.

[0071] A photo-interrupter 215 is secured to the fixed tube 201 with ascrew after it is soldered to a circuit board 216. The photo-interrupter215 is arranged to detect the datum position of the second lens tube 205with a light blocking wall part 205 b which is formed integrally withthe second lens tube 205 passing through an interval between the lightprojecting part and the light receiving part and to allow the zoom motor209 to move the second lens tube 205 to each zooming position accordingto the number of pulses inputted to the zoom motor 209. Focus adjustmentis also likewise arranged to be made by detecting a light blocking wallpart 207 b of the fourth lens tube 207 as a datum position with aphoto-interrupter 217 and a circuit board 218 which are mounted on therear tube 202 and by driving the focus motor 212 stepwise as necessary.

[0072] The image shake correcting unit 204 is arranged as follows.

[0073]FIG. 13 is an exploded perspective view of the image shakecorrecting unit 204 in the second embodiment. In FIG. 13, referencenumeral 240 denotes a fixed frame. The fixed frame 240 is provided withtwo bosses 240 a (see FIG. 12) for positioning the fixed frame 240 withrespect to the fixed tube 201 and two bosses 240 b for positioning thefixed frame 240 with respect to the rear tube 202. The image shakecorrecting unit 204 is thus carried jointly by the fixed tube 201 andthe rear tube 202. A moving frame 241 is arranged to hold the third lensunit L3, which is an image shake correction lens.

[0074] The moving frame 241 is provided with three holes 241 a in itsperiphery with pins 242 secured to the holes 241 a. The pins 242 arefitted into slots 240 c of the fixed frame 240. The moving frame 241 isarranged to be movable in a direction perpendicular to the optical axiswithin a predetermined range with respect to the fixed frame 240 as thepins 242 are thus arranged to smoothly slide in the slots 240 c.

[0075] The pins 242 and the slots 240 c corresponding to them are evenlyspaced at intervals of 120° within one and the same plane and arearranged in a balanced state to have no moment around the optical axiscaused to act on the moving frame 241 by a load brought about by anysliding friction. A roll preventing plate 244 is arranged to prevent themoving frame 241 from turning around the optical axis in correctingimage shakes. The roll preventing plate 244 is provided with slots 244 aand 244 b which are fitted on a boss 240 e provided on the fixed frame240 and a boss which is not shown. Other slots 244 c and 244 d providedalso in the roll preventing plate 144 are fitted on bosses (not shown)which are provided on the moving frame 241. Hole parts 244 e and 244 fwhich are provided in the roll preventing plate 244 for allowing supportposts 240 f and 240 g formed integrally with the fixed frame 240 topierce through these hole parts. The arrangement is such that, even ifthe roll preventing plate 244 moves to its maximum extent, the supportposts 240 f and 240 g do not interfere with the roll preventing plate244. In other words, the roll preventing plate 244 is arranged to moveonly in the vertical direction as viewed in FIG. 13 with respect to thefixed frame 240 while the moving frame 241 is arranged to be movableonly horizontally as viewed in FIG. 13 with respect to the rollpreventing plate 244. The combination of these moving directions enablesthe moving frame 241 to move vertically and horizontally as viewed inFIG. 13 without turning or rolling around the optical axis with respectto the fixed frame 240.

[0076] A method for driving the moving frame 241 is next described.

[0077] Coils 245 a and 245 b which are secured to the moving frame 241are provided for driving the moving frame 241 in the horizontaldirection (hereinafter referred to as the X direction) and in thevertical direction (hereinafter referred to as the Y direction). Magnets246 a and 246 b are respectively magnetized to have two poles in the Xand Y directions. The magnets 246 a and 246 b are secured to the fixedframe 240 and fixed in position with lower yokes 247 a and 247 b whichare made of iron or the like arranged to attract them from behind thefixed frame 240 to cause them to be inserted respectively through holeparts 240 h and 240 i of the fixed frame 240. An upper yoke 248 which ismade of the same material as the lower yokes 247 a and 247 b is securedwith screws 253 to the support posts 240 f and 240 g of the fixed frame240 from its front side together with a sensor holder 249 which will bedescribed later. The upper yoke 248 is thus arranged to form a magneticcircuit for driving in the X and Y directions. More specifically, amagnetic circuit is formed for driving in the X direction jointly by themagnet 246 a, the lower yoke 247 a and the upper yoke 248 with the coil245 a inserted in the magnetic circuit. Another magnetic circuit isformed for driving in the Y direction jointly by the magnet 246 b, thelower yoke 247 b and the upper yoke 248 with the coil 245 b insertedtherein. An electromagnetic actuator of the moving coil type is formedin this manner.

[0078] Light projecting elements 250 a and 250 b are IREDs or the like.Light receiving elements 251 a and 251 b are PSDs or the like. Theseelements are inserted into the sensor holder 249 from its peripheralside and are fixed in position by bonding. Narrow slits 241 c and 241 dwhich are formed integrally with the moving frame 241 are inserted inbetween each of the pairs of the light-projecting and light-receivingelements. Of infrared light rays projected from the light projectingelements 251 a and 251 b, only the infrared rays passing through theslits 241 c and 241 d are received by the light receiving elements 251 aand 251 b. The positions of the moving frame 241 in the X and Ydirections are detected by using the infrared rays thus received. Thelight projecting elements 250 a and 250 b and the light receivingelements 251 a and 251 b are connected to a flexible printed circuitboard 252 (shown in a divided state in FIG. 13) and are thus connectedto a control circuit provided on the side of a camera body which is notshown. The wiring of the coils 245 a and 245 b is connected to a drivingcircuit which is also disposed on the side of the camera body.

[0079] The diaphragm unit in the second embodiment is next described.

[0080]FIG. 14 is a plan view of the IG meter unit 208. The IG meter unit208 includes the diaphragm blades 803 and 804 which constitute the firstdiaphragm means. The diaphragm blades 803 and 804 are held by a fixedframe 801 to be movable in parallel with each other in the verticaldirection as viewed in FIG. 14, in a state of being guided by the bosses801 a and 801 b which are formed integrally with the fixed frame 801.Bosses 805 a and 805 b are provided on an arm 805 which is arrangedintegrally with the rotating shaft of a meter 800. The bosses 805 a and805 b engage slots 803 a and 804 a which are provided respectively inthe diaphragm blades 803 and 804. ND filters 806 and 807 are attached tothe diaphragm blades 803 and 804 by bonding. The ND filters 806 and 807are thus arranged to reduce a light quantity to prevent the aperturediameter from becoming a predetermined aperture diameter because thequality of images deteriorates due to an adverse effect of diffractionif the aperture diameter becomes too small. To prevent the ND filters806 and 807 from coming into sliding contact with the diaphragm blades803 and 804, the ND filters 806 and 807 are disposed respectively infront of the diaphragm blade 803 which is located on the front side ofthe optical axis and in rear of the diaphragm blade 804.

[0081] When the diaphragm blades 803 and 804 are fully opened, the NDfilters 806 and 807 are in a state of being located at an optical path.The ND filters 806 and 807 come to completely cover the optical pathwhen the aperture reaches a predetermined aperture value position. Whenthe aperture is further stopped down, the aperture is completely coveredby the diaphragm blades 803 and 804. Further, the two upper and lower NDfilters 806 and 807 are arranged to simultaneously enter the opticalpath to make the variation of the peripheral light quantity on the imageplane uniform in correcting image shakes.

[0082]FIG. 15 shows the arrangement of the second diaphragm means in thesecond embodiment. In FIG. 15, reference numeral 820 denotes six blades.Each of the blades 820 is swingably carried by the fixed frame 801 withits hole part 820 a engaging a boss 801 c provided on the fixed frame801. Each of the blades 820 is provided with a slot 820 b which engagesone of bosses 821 a provided on a ring 821 which is arranged to berotatable around the optical axis. The ring 821 has a slot 821 b formedin a part extending from its periphery. The slot 821 b of the ring 821engages a boss 823 a of an arm 823 which is fixedly attached to therotating shaft of a second diaphragm driving meter 822. Therefore, therotation torque of the meter 822 is transmitted through the arm 823 tothe ring 821 to cause the ring 821 to rotate. The rotation of the ring821 causes the six blades 820 to swing on the holes 820 a in such a wayas to vary the aperture diameter.

[0083] The second diaphragm means is thus arranged to vary the diameterof an aperture according to the zooming position of the lens systemirrespective of the quantity of light. In correcting image shakes, thesecond diaphragm means serves to alleviate variations taking place inthe peripheral light quantity on the image plane. In the case of theimage-shake correction by the shift method, the correction lens isdisposed inside the optical system. Therefore, a peripheral light fluxis determined by an optical system disposed in front of the correctionlens. The quantity of peripheral light then varies when the light fluxis bent by the correction lens at the time of image shake correction. Inmost of zoom lenses, a light flux is restricted on the side of atelephoto end by the effective diameter of a front lens. Therefore, adifference in light quantity between a central part and a peripheralpart of an image plane increases on the side of the telephoto end. Inview of this, the second embodiment is arranged to appositely restrictthe peripheral light flux by lessening the aperture diameter of thediaphragm accordingly as the position of the optical system shifts fromits wide-angle side toward its telephoto end in such a way as toalleviate a change of the peripheral light quantity even when thecorrection lens is shifted.

[0084]FIGS. 16 and 17 are graphs showing the peripheral light quantityobtained by shifting the correction lens at the telephoto end. In eachof these graphs, positions from the center of the image plane are shownin the horizontal direction and the quantities of light in the verticaldirection. FIG. 16 shows the peripheral light quantity obtained withoutusing the second diaphragm means. FIG. 17 shows the peripheral lightquantity obtained with the second diaphragm means used. In each of FIGS.16 and 17, a broken line shows a state of having the correction lens atthe center of the optical axis, and a full line shows a state of havingthe correction lens shifted. The state of the full line and the state ofthe broken line are considered to appear one after another while theimage shake correction is in process. Therefore, luminance differencesindicated with a reference symbol A appear one after another in theperipheral part of the image plane to give a disagreeable impression tothe eye. As shown in FIGS. 16 and 17, although the absolute lightquantity becomes less in the case of FIG. 17 with the second diaphragmmeans used than in the case of FIG. 16, the change A of the peripherallight quantity which takes place at the time of image shake correctioncan be lessened by the use of the second diaphragm means in the case ofFIG. 17.

[0085] To avoid having the peripheral light quantity unnaturally vary atthe time of image shake correction, the aperture is preferably arrangedto be in a shape as close to a circle as possible. Further, in FIG. 14,a two-dot-chain line 808 represents an aperture shape of the seconddiaphragm means obtained in the telephoto end. The aperture is shaped insuch a way as to be not affected by the ND filters 806 and 807 in thetelephoto end even in a case where the diameter of the aperture 808 ofthe second diaphragm means is variable.

[0086] Control over the image shake correcting unit 204 and thediaphragm unit 208 is next described as follows.

[0087]FIG. 18 shows a system provided for the above control. Amicrocomputer 70 is arranged to preside over the control of the wholecontrol system. A vibration sensor 71 is composed of a vibration gyro,etc., and is arranged to detect vibration of the camera as an angularvelocity or an angle.

[0088] The microcomputer 70 computes the amount of vibration of thecamera on the basis of a detection signal obtained from the vibrationsensor 71 and computes a target (or objective) position of thecorrection lens L3 at which an image shake resulting from the vibrationof the camera can be canceled. Then, according to the result ofcomputation of the amount of movement, the coils 245 a and 245 b of theelectromagnetic actuator are energized to drive the correction lens L3.In driving the correction lens L3, the position of the correction lensL3 is detected by correction lens position sensors 50 and 51. The resultof such detection is fed back to the microcomputer 70, so that thecorrection lens L3 can be accurately driven and moved to the targetposition computed.

[0089] In the zoom lens, the amount of movement (the target position) ofthe correction lens L3 for canceling an image shake varies according tothe focal length. In view of this, the number of pulses with which thesecond lens unit L2 is driven is counted to detect the focal length by azoom position sensor 72. Then, the amount of driving of the correctionlens L3 is adjusted according to the focal length detected.

[0090] A light quantity sensor 73 is arranged to detect the quantity oflight from a video signal obtained by the CCD. The microcomputer 70causes the diaphragm blades 803 and 804 to be driven by energizing thefirst diaphragm driving meter 800 to obtain a predetermined quantity oflight on the basis of a detection signal received from the lightquantity sensor 73. Meanwhile, the second diaphragm driving meter 822 isenergized to drive the blades 820 in such a way as to obtain apredetermined aperture diameter.

[0091] The second embodiment is arranged, as described above, toappositely restrict an on-axial light flux on the telephoto side (notrestricting it on the wide-angle side) by the second diaphragm meansaccording to the zoom position. Although the absolute quantity of lightis decreased thereby, the variations taking place in the peripherallight quantity at the time of image shake correction is effectivelylessened by this arrangement, so that image shakes can be correctedwithout causing images to give any disagreeable impression.

[0092] Further, in the second embodiment, the ND filter mounted on thefirst diaphragm means is prevented from coming partly into the opticalpath to bring about any asymmetric variations of the peripheral lightquantity, so that images can be prevented from becoming unnatural.

[0093]FIGS. 19 and 20 show a diaphragm unit of an optical apparatusaccording to a third embodiment of the invention. The basic arrangementof the third embodiment is identical with that of the second embodiment.All the component elements of the third embodiment that are the same asthose of the second embodiment are, therefore, indicated by the samereference numerals as those of the second embodiment, and details ofthem are omitted from the following description.

[0094]FIG. 19 shows in a plan view the second diaphragm means in thethird embodiment. In FIG. 19, reference numeral 820 indicates six bladeswhich are arranged in the same manner as in the second embodiment. Holeparts 820 a of the blades 820 engage the bosses 851 c provided on thefixed frame 851, so that the blades 820 are swingably carried. Theblades 820 are provided with slots 820 b which engage the bosses 852 aprovided on the ring 852 which is arranged to be rotatable around theoptical axis.

[0095] As in the second embodiment, the third embodiment is alsoarranged to be capable of varying the aperture diameter by the rotationof the ring 821. In this case, however, the aperture diameter isarranged to be varied in association with the movement of the secondlens tube 501 which is provided for zooming, instead of using theelectromagnetic actuator.

[0096] In FIG. 19, only the sleeve part 501 a of the second lens tube501 is illustrated. The sleeve part 501 a is provided with an end facecam 501 b. The ring 852 has an arm part 852 b extending from itsperiphery. The arm part 852 has an end face 852 c. The rotating positionof the ring 852 is restricted with the end face 852 c arranged to abuton the end face cam 501 b of the sleeve part 501 a of the second lenstube 501. A tension coil spring 853 is attached at its one end to a hook852 d which protrudes from the arm part 852 b. The other end of thespring 853 is attached to a projection 851 d provided on the fixed frame851. The coil spring 853 is thus arranged to constantly urge the endface 852 c of the ring 852 to be pushed against the end face cam 501 bof the sleeve part 501 a.

[0097]FIG. 20 is an exploded perspective view of the third embodiment.As shown in FIG. 20, the front side of the end face cam 501 b of thesecond lens tube 501 is in a shape which greatly protrudes forward.Therefore, the ring 852 comes to rotate against the urging force of thespring 853 to reduce the size of aperture formed by the blades 820accordingly as the second lens tube 501 moves rearward, i.e., toward thetelephoto end.

[0098] Since the arrangement of the third embodiment obviates thenecessity of using an actuator for driving the blades, unlike in thecase of the second embodiment, the third embodiment can be more simplyarranged and also contributes to reduction in electric energyconsumption.

[0099] While the third embodiment uses a moving coil type actuator fordriving the correction lens, the same advantageous effect can beattained by replacing this actuator with a motor or an electrostrictiveelement or some other electromagnetic actuator.

[0100] Further, to have an aperture shape close to a circle andlaterally and vertically symmetrical, the first diaphragm of thediaphragm unit is arranged to have two parallel moving blades and two NDfilters attached thereto. The second diaphragm of the diaphragm unit isarranged, also for the same purpose, to have six blades. However,according to the invention, the diaphragm unit is not limited to thearrangement disclosed. For example, both the first and second diaphragmsmay be arranged to be composed of six blades or to be using two swingingtype blades.

[0101] The arrangement of the third embodiment obviates the necessity ofusing an actuator for driving the second diaphragm means, so thatdeterioration of images at the time of image shake correction can beminimized with simple structural arrangement.

[0102] According to the arrangement of each of the second and thirdembodiments, a lens barrel or an optical apparatus using the lens barrelcan be arranged to be suited for a high magnification zoom lens whichnever deteriorates its optical performance for an entire image planeeven while image shake correction is in process.

[0103] A particularly advantageous feature of each of the second andthird embodiments lies in the provision of the second diaphragm meanswhich is arranged, in addition to an ordinary diaphragm (the firstdiaphragm means), to give a predetermined aperture diameter according tothe zooming position of the optical system. In accordance with theinvention, the second diaphragm means may be arranged to be driven by ameter by detecting a zooming position from the driving pulses of thelens barrel or to be driven according to the movement of a variator lenstube in a mechanically interlocked state. By such an arrangement, theperipheral light flux can be appositely limited according to zooming, sothat the luminance variations taking place in the peripheral part of animage plane at the time of image shake correction can be lessened overthe whole range of zooming.

[0104] A description will now be given of a different embodiment of theinvention. In the foregoing description, an aperture diaphragm isspecifically mentioned as being the light-quantity control device. Theuse of an aperture diaphragm as the light-quantity control device,however, is only illustrative and the invention may be implemented byincorporating different types of light-quantity control devices asdescribed below. Embodiments employing such light-quantity controldevices will now be described.

[0105]FIG. 21 is an illustration of a light-quantity control device usedin an embodiment of the present invention.

[0106] Referring to this figure, the embodiment incorporates aliquid-crystal diaphragm 1001 constituted by a liquid crystal device forcontrolling the amount of light flux, i.e., luminous flux, passingthrough the optical system. The liquid-crystal diaphragm 1001 has aplurality of annular areas 1001 a and 1001 b which are centered at theoptical axis of the optical system. The areas 1001 a and 1001 b areconnected to a driver circuit 1002 which drives these areas 1001 a and1001 b so that these areas 1001 a and 100 b area switched between an OFFstate in which the liquid crystal transmits light rays and an ON statein which the liquid crystal blocks light rays. The driver circuit 1002performs the ON/OFF control of the areas 1001 a and 1001 b in accordancewith signals which are derived from a CPU of a video camera (not shown)and which indicates the shake-proofing state. The liquid-crystaldiaphragm 1001 may be mounted in place of and at the same position asthe diaphragm 5 of the preceding embodiments shown in FIGS. 1 and 5. Theliquid-crystal diaphragm 1001 also may be mounted in place of and at thesame position as the second diaphragm 820 of the preceding embodimentsshown in FIGS. 11 and 18. It is still possible to employ theliquid-crystal diaphragm in a lens system other than the described zoomlens devices, e.g., in a single-focus telephoto lens system.

[0107] The liquid-crystal diaphragm 1001 shown in FIG. 21, when used ina zoom lens device, operates in a manner described below. The drivercircuit 1002, upon receipt of a shake-proofing operation start signal isreceived from the video camera, sets the area 10011 a and 1001 b to theON or OFF state in accordance with a zoom position signal given by thezoom lens device. If, for instance, the zoom signal indicates atelephoto-end focal length, the areas 1001 a and 1001 b are set to theON state, whereas, when the zoom signal indicates a focal length rangingbetween medium and wide-angle end, the area 1001 a is set to the ONstate, while the area 1001 b is set to the OFF state. As theliquid-crystal diaphragm 1001 is driven in the manner described, theon-axis luminous flux (light flux) reaching the central region of theimage field is blocked, as in the cases of the preceding embodiments,whereby the difference in brightness between the central region and theperipheral region of the image field on the focal plane of the imagepickup device can be diminished. This serves to remarkably reduce thevariation in the brightness of the image field during the shake-proofingoperation in which a shift lens for camera shake is actuated.

[0108] A description will now be given of a still different embodimentof the present invention, with reference to FIG. 22, which is anillustration of the light-quantity control device used in thisembodiment and also to FIGS. 23A and 23B, which show light-quantitydistributions.

[0109] Referring to FIG. 22, this embodiment has an image taking lensdevice which may be a zoom lens unit having a variable magnificationlens, or single-focal telephoto lens unit. The image taking lens device1101 has a shift lens 1012 which is shiftable to compensate for theundesirable effects caused by a camera shaking. A CCD 1013 serving as animage pickup device is disposed at the focal plane of the image takinglens 1011. Picture signals from the CCD 1013 are delivered to a cameraprocess circuit when performs processing of the picture signals.

[0110] Referring further to FIG. 22, the embodiment has a microcomputerwhich is responsible for the overall control of the whole device, and ashake or shake sensor comprising, for example, a vibrating gyroscope,for sensing shaking of an image take-up device, such as a video camera,in terms of angular velocity or angle. The embodiment further has anactuator for actuating the shift lens 1012 in horizontal and verticaldirections with respect to the optical axis of the image taking lens1011. The actuator 1016 may be, for example, a voice coil motor. Numeral1017 designates a gain controller for controlling the gain of pixeloutput signals on a pixel block basis: namely, for every block having aplurality of pixels of the CCD 1013. A memory 1013 stores informationconcerning the distribution of the light quantity that was created bythe entire light flux obtained through the image taking lens 1011 andthat is observed at the focal plane on the CCD 1013. The arrangement issuch that information concerning the light quantity distribution on theCCD 1013, which will be obtained if the shift lens 1012 is moved to acertain position for the shake correction in response to a shake signalfrom the shake sensor 1015, is output from the memory 1018 to themicrocomputer 1014 in relation to the level of the shake signal. Thelight quantity information stored in the memory 1018 will be describedwith reference to FIGS. 23A and 23B. FIG. 23A shows the light quantitydistribution on the focal plane of the CCD 1013 provided by the wholelight flux obtained through the image taking lens 1011, in the shakecorrection OFF state in which the shift lens 1012 is located on theoptical axis of the optical system. Representing the light quantity atthe cental region around the optical axis by 100%, the light quantity isprogressive decreased radially outward, as indicated by 80%, 60%, 40%and 20%. The imaging effective area 1013 a of the CCD 1013 receiveslight fluxes coming through the region central region around the opticalaxis, so that the light quantity arranges from 80% to 100%. FIG. 23Bshows the light quantity distribution as observed in the shakecorrection ON state in which the shaft lens 1012 of the imaging takinglens 1011 has been moved so as to effect the shaft correction inaccordance with the shake signal derived from the shake sensor 1015. Inthis case, a light quantity distribution is created such that the lightquantity received by the effective imaging area 1013 a of the CCD 1013progressive decreases from 100% to 40% along a line extending betweenthe left upper corner and the right lower corner as viewed in thedrawing. Information concerning this light quantity distributiondeveloped by the light fluxes impinging upon the effective imaging area1013 a of the CCD 1013, obtained when the shift lens 1012 has beenshifted in response to the shake signal derived from the shake sensor1015, is stored in the memory table in relation to the level of theshake signal.

[0111] The operation of this embodiment is as follows. When the shakecorrection in ON, a shake signal from the shake sensor 1015 is input tothe microcomputer 1014, so that the microcomputer 1014 drives theactuator 1016 in accordance with the shake signal, thereby shifting theshift lens 1012 to compensate for any undesirable effect caused by acamera shake. In the meantime, the microcomputer 1014 reads, from thememory table for the memory 1018, the information concerning the lightquantity distribution on the effective imaging area 1013 a of the CCD1013 created when the shift lens 1012 has been shifted in response tothe shake signal produced by the shake sensor 1015. Based on the lightquantity distribution information read from the memory 1018, themicrocomputer 1014 drives the gain controller 1017 so as to control thegains for the output signals produced by the pixels in the effectiveimaging area 1013 a of the CCD 1013. For instance, if the shift lens1012 has been shifted to the position shown in FIG. 23B, the lightfluxes reaching the effective imaging area 1013 a of the CCD 1013 createthe light quantity distribution in which, as stated before, the lightquantity progressively decreases from 100% to 40% along a line extendingbetween the left upper corner and the right lower corner as viewed inthe drawing. In this case, the microcomputer 1014 operates on the gainsfor the output signals from the pixels in the regions receivingdifferent light quantities, such that a uniform light quantitydistribution is developed over the entire effective imaging area 1013 a.More specifically, the microcomputer 1014 drives the gain controller1017 so as to reduce the gains for the output signals from the pixels inthe regions where the light quantities are 100%, 80% and 60% so that thelight quantity of 40% is obtained over the entire effective imaging area1013 a.

[0112] Thus, the gain controller 1017 is driven in such a manner that auniform light quantity distribution is developed over the entireeffective imaging area 1013 a of the CCD 1013, whereby the generation ofan unnatural image caused by a variation in the light quantity during ashake-proofing operation can effectively be avoided.

[0113] The embodiment shown in FIG. 22 is arranged such that the gainsof the output signals from the pixels of the CCD 1013 are directlycontrolled by the gain controller 1017. This, however, is not exclusiveand the arrangement may be such that the analog output signals from thepixels of the CCD 1013 are converted into digital picture signals andthe resultant -digital picture signals are rearranged in a frame memory.In this case, the gain controller effects the control operation so as tovary the gains for the digital picture signals that correspond to thepixels of the CCD 1013 and that have been arranged on the frame memory.

[0114] A description will now be given of a further different embodimentof the present invention, with specific reference to FIGS. 24 and 25,which are an illustration of a light quantity control device used inthis embodiment and an illustration of a light quantity distribution,respectively. The embodiment described with reference to FIG. 22 reliesupon an optical shake-proofing measure in which shake proofing iseffected by mechanically shifting the shift lens. In contrast, theembodiment which will now be described with reference to FIG. 24 employsan electronic shake-proofing technique that electrically performs theshake-proofing operation.

[0115] Referring to FIG. 24, an image taking lens 1021 is an image takelens device that may be a zoom lens device having a magnification lensor a single-focus telephoto lens device. The image taking lens 1021 hasa fixed image forming lens 1022. A CCD 1023 as an image pickup device isdisposed at the focal plane of the image taking lens 1021. Picturesignals from the CCD 1023 are delivered to a camera process circuit thatperforms various processing operations on the picture signals. As willbe seen from FIG. 25, the CCD 1023 has a full imaging area 1023 acarrying, for example, 680,000 pixels. The arrangement is such that theoutput signals from pixels in an output imaging area 1023 b which is aregional area cut out from the full imaging area 1023 a is constitutedby, for example, 350,000 pixels.

[0116] Referring to FIG. 24, the embodiment employs a microcomputer 1024which is responsible for the overall control of the whole apparatus, anda shake sensor 1025, which may be a vibrating gyroscope and whichdetects shaking of the image taking device, such as a video camera interms of angular velocity or angle. The embodiment further includes acut-off position designating circuit, which designates the position ofthe output imaging area 1023 b to cut off the full imaging area 1023 aof the CCD 1023. A memory 1028 stores information concerning the lightdistribution developed at the focal plane on the CCD 1023 by the lightfluxes coming through the image taking lens 1021. The arrangement issuch that the microcomputer 1024 reads from the memory 1028 theinformation concerning light quantity distribution on the output imagingarea 1023 b cut off the full imaging are 1023 a of the CCD, inaccordance with a shake signal produced by the shake sensor 1025.

[0117] The nature of the light quantity distribution information storedin the memory 1028 will be described in more detail with reference toFIG. 25.

[0118] This figure shows a light quantity distribution developed on theentire part of the full imaging area 1023 a of the CCD 1023, produced bythe whole light fluxes coming through the image taking lens device 1021when the shake-proofing function is OFF. Representing the light quantityat the central region around the optical axis by 100%, the lightquantity progressively decreased radially outward, as indicated by 80%,60%, 40% and 20%. Thus, the imaging area is brightest at the centralregion and is darkened towards the peripheral end. When theshake-proofing function is OFF, the center of the output imaging area1023 b coincides with the optical axis. In this state, the outputimaging area 1023 b receives light fluxes coming along the centralregion around the optical axis, so that the light quantity on the outputimaging area 1023 b ranges from 80% to 100%.

[0119] Referring to FIG. 25, the position of the output imaging area1023 b cut off the full imaging area 1023 a of the CCD 1023 has beenshifted to a position “A” indicated by a broken line in accordance witha shake signal derived from the shake sensor 1025, so as to effect theshake correction. In this state, the light fluxes impinging upon theoutput imaging area 1023 b provide a light quantity distribution suchthat the light quantity progressively decreases from 100% to 40% along adiagonal line extending between the left upper corner to the right lowercorner of the area 1023 a as viewed in the figure. Informationconcerning this light quantity distribution created on the shiftedoutput imaging area 1023 b is stored in the memory table in relation tothe shake signal which is derived from the shake sensor 1025 and whichcorresponds to this light quantity distribution.

[0120] In operation, when the shake correction function is OFF, theshake signal from the shake sensor 1025 is input to the microcomputer1024. The microcomputer 1024 operates to vary the position on the fullimaging area 1023 a at which the output imaging area 1023 b is to be cutoff the full imaging area 1023, in accordance with the shake signalreceived from the shake sensor 1025, whereby a shake correction isperformed to compensate for the undesirable effects produced by camerashaking.

[0121] The microcomputer also reads, from the memory table of the memory1028, the information concerning the distribution of the light quantitycreated by the light fluxes impinging upon the output imaging area 1023b that has been shifted in accordance with the shake signal. Themicrocomputer 1024 then drives the gain controller 1027 so as tocontrol, based on the light quantity distribution information read fromthe memory 1028, the gains for the output signals from the pixelscontained in the output imaging area 1023 b of the CCD 1023.

[0122] For instance, if the cut-off position, i.e., the position of theoutput imaging area 1023 b, has been shifted to the position “A”indicated by the broken line in FIG. 25, the light quantity distributioncreated by the light fluxes reaching the shifted output imaging area1023 b progressively decreases from 100% to 40% along the diagonal linestarting from the left upper corner and terminating at the right lowercorner. In this case, the microcomputer 1024 drives the gain controllerso that gains are suitably reduced for the output signals from thepixels in the regions where the light quantities are 100%, 80% and 60%,such that a uniform light quantity of 40% is developed over the entiretyof the output imaging are 1023 b.

[0123] Thus, in this embodiment, the gain controller 1027 is activatedin accordance with the shake signal, so as to achieve a uniform lightquantity distribution over the output imaging area 1023 b cut off thefull imaging area 1023 a of the CCD 1023. It is therefore possible toavoid generation of an unnatural image attributable to a variation inthe light quantity distribution which occurs during the shake-proofingoperation.

[0124] The embodiment shown in FIG. 24 is arranged such that the gainsof the output signals from the pixels of the CCD 1023 are directlycontrolled by the gain controller 1027. This, however, is not exclusiveand the arrangement may be such that the analog output signals from thepixels of the CCD 1023 are converted into digital picture signals andthe resultant digital picture signals are rearranged in a frame memory.In this case, the gain controller effects the control operation so as tovary the gains for the digital picture signals which correspond to thepixels of the CCD 1023 and which have been arranged on the frame memory.The light quantity distribution on the full imaging area 1023 a of theCCD 1023 provided by the light fluxes coming through the image takinglens 1021 is not changed regardless of whether the shake-proofingfunction is ON or OFF. Therefore, the embodiment described withreference to FIG. 24 may be modified such that, when the shake-proofing-function is ON, the gain controller 1027 performs a gain control forall the pixels of the full imaging area 1023 a so as to realize an equallight quantity, e.g., 40%, over the entire full imaging area 1023 a.

1. An image stabilizer for an image taking lens device, comprising:image stabilizing means operative for stabilizing, during shaking of theimage taking lens device, the image generated by said image taking lensdevice; light quantity control means disposed in the light path of saidimage taking lens device; and controlling means for controlling saidlight quantity control means so as to vary the aperture size of saidlight quantity control means during the image stabilizing operationperformed by said image stabilizing means.
 2. An image stabilizeraccording to claim 1, wherein said light quantity control meanscomprises a diaphragm having a plurality of diaphragm blades driven tovary the aperture size, and wherein said controlling means operates soas to drive said diaphragm blades to reduce said aperture size, duringthe image stabilizing operation performed by said image stabilizingmeans.
 3. An image stabilizer according to claim 1, wherein said lightquantity control means comprises a liquid crystal device having annularregions coaxial with the optical axis of said image taking lens device,and wherein said controlling means drives said liquid crystal device soas to reduce the aperture size, during the image stabilizing operationperformed by said image stabilizing means.
 4. An image stabilizer for animage taking lens device, comprising: image stabilizing means operativefor stabilizing, during shaking of the image taking lens device, theimage generated by said image taking lens device; an image pickup devicedisposed at the imaging plane of said image taking lens device andhaving an imaging area which converts an optical image formed by saidimage taking lens device into electrical signals, said image pickupdevice delivering as picture signals the electrical signals derived fromsaid imaging area; light quantity correcting means for correcting thelight distribution of the image formed by the pixel signals delivered bysaid image pickup device; and controlling means for causing said lightquantity correcting means to effect a correction of the light quantitydistribution during the image stabilizing operation performed by saidimage stabilizing means.
 5. An image stabilizer according to claim 4,further comprising a shake sensor for sensing shaking of said imagetaking lens device, wherein said image stabilizing means comprises ashake correction lens and an actuator for actuating said shakecorrection lens, wherein said light quantity correcting means comprisesa gain controller for controlling the gains for the pixels contained insaid imaging area of said image pickup device, and wherein saidcontrolling means controls said gain controller such that said gaincontroller varies the gains for pixels of said imaging area inaccordance with a shake signal from said shake sensor, when said shakecorrection lens is being actuated by said actuator.
 6. An opticalapparatus having an image taking lens device, comprising: a sensor forsensing shaking of said optical apparatus, said sensor outputting ashake signal corresponding to a shaking of said optical apparatus; ashake correction lens provided in said image taking lens device, saidshake correction lens being movable in directions perpendicular to theoptical axis of said image taking lens device; an actuator for actuatingsaid shake correction lens in accordance with the shake signal from saidsensor; an image pickup device provided on the imaging plane of saidimage taking lens device, for converting an optical image formed by saidimage taking lens device into electrical signals and delivering theelectrical signals as picture signals; light quantity correction meansfor correcting the light quantity distribution of the image to be formedby said picture signals delivered by said image pickup device; andcontrolling means for controlling said light quantity correcting meansso as to effect a correction of the light quantity distribution whensaid shake correction lens is being actuated by said actuator.
 7. Anoptical apparatus having an image taking lens device, comprising: asensor for sensing a shaking of said optical apparatus, said sensoroutputting a shake signal corresponding to the shaking; a shakecorrection lens provided in said image taking lens device, said shakecorrection lens being movable in directions perpendicular to the opticalaxis of said image taking lens device; an actuator for actuating saidshake correction lens in accordance with the shake signal from saidsensor; an image pickup device provided on the imaging plane of saidimage taking lens device, for converting an optical image formed by saidimage taking lens device into electrical signals and delivering theelectrical signals as picture signals; a diaphragm disposed in the lightpath of said image taking lens device; and controlling means forperforming control so as to vary the aperture size of said diaphragmwhen said shake correction lens is being actuated by said actuator, suchthat the aperture size of said diaphragm is smaller when said shakecorrection lens is being actuated than when said shake correction lensis not being actuated.
 8. An optical apparatus having an image takinglens device, comprising: a sensor for sensing a shaking of said opticalapparatus, said sensor outputting a shake signal corresponding to theshaking; a shake correction lens provided in said image taking lensdevice, said shake correction lens being movable in directionsperpendicular to the optical axis of said image taking lens device; anactuator for actuating said shake correction lens in accordance with theshake signal from said sensor; an image pickup device provided on theimaging plane of said image taking lens device and having an imagingarea for converting an optical image formed by said image taking lensdevice into electrical signals and delivering the electrical signalsfrom said imaging area as picture signals; a gain controller forcontrolling the gains for the pixels contained in said imaging area ofsaid image pickup device; and controlling means for controlling, inaccordance with the shake signal from said sensor, said gain controllerso as to vary the gains for the pixels of said imaging area of saidimage pickup device when said shake correction lens is being actuated bysaid actuator.
 9. An optical apparatus having an image taking lensdevice, comprising: an image pickup device provided at the imaging planeof said image taking lens device, for converting an optical image formedby said image taking lens device into electrical signals, said imagepickup device having a full imaging area and an output imaging areanarrower than said full imaging area; a sensor for sensing a shaking ofsaid optical apparatus and for producing a shake signal corresponding tothe shaking; shake correcting means for effecting a correction of animage shaking by shifting, in accordance with the shake signal from saidsensor, said output imaging area to be read out from said full imagingarea of said image pickup device; light quantity correcting means forcorrecting the light quantity distribution on the image in said outputimaging area read out from said full imaging area of said image pickupdevice; and controlling means for performing control such that thecorrection of the light quantity distribution by said light quantitycorrecting means is executed during the correction of the shaking of theimage performed by said shake correcting means.
 10. An optical apparatushaving an image taking lens device, comprising: an image pickup deviceprovided at the imaging plane of said image taking lens device, forconverting an optical image formed by said image taking lens device intoelectrical signals, said image pickup device having a full imaging areaand an output imaging area narrower than said full imaging area; asensor for sensing a shaking of said optical apparatus and for producinga shake signal corresponding to the shaking; shake correcting means foreffecting a correction of image shaking by shifting, in accordance withthe shake signal from said sensor, said output imaging area to be readout from said full imaging area of said image pickup device; a diaphragmprovided in the light path of said image taking lens device; andcontrolling means for performing control so as to vary the aperture sizeof said diaphragm during the correction of the shaking of the imageperformed by said shake correcting means, said controlling meansperforming control such that the aperture size of said diaphragm issmaller when the image shake correcting operation is being performed bysaid shake correcting means than when the image shake correctingoperation is not being performed.
 11. An optical apparatus having animage taking lens device, comprising: an image pickup device provided atthe imaging plane of said image taking lens device, having an imagingarea for converting an optical image formed by said image taking lensdevice into electrical signals, said image pickup device having anoutput imaging area narrower than said imaging area and delivering theelectrical signals from said output imaging area as picture signals; asensor for sensing a shaking of said optical apparatus and for producinga shake signal corresponding to the shaking; shake correcting means foreffecting a correction of image shaking by shifting, in accordance withthe shake signal from said sensor, said output imaging area to be readout from said imaging area of said image pickup device; a gaincontroller for controlling the gains for the pixels of said imaging areaof said image pickup device; and controlling means for controlling saidgain controller so as to vary the gains for the pixels of said imagingarea of aside image pickup device during the correction of the shakingof the image performed by said shake correcting means.